Impact printers have traditionally been used to create point-of-sale (POS) receipts in the form of a hardcopy printout for the purchaser. Such receipts typically list the item description and price for each purchase in order to create a subtotal, with any sales tax or discount also tabulated in order to create a final total cost. Additional date, location, store name, and promotional messages are usually also shown on the receipt, as well as the details of payment such as cash tendered, credit card type and account number, etc.
The goal is to display all of the above-identified information legibly on a small size piece of plain paper which is printed in an efficient, reliable and inexpensive manner. Impact printers often do not consistently produce legible receipts, and in many instances are rather noisy. Accordingly there is a need to adapt inkjet printing technology for use in creating POS receipts without having to use an excessive amount of ink.
An ink-efficient format for a customized font in a printing system for printing alphanumeric data and symbols. The customized font can be implemented using a relatively low resolution printhead for creating digitized characters in precise pixel grid locations on media such as a hardcopy receipt. Each character is formed in a block of predetermined size called herein a hybrid cell having a central printable portion and certain non-printable perimeter portions. A preferred hybrid cell incorporates a pixel grid having a higher resolution in a printing scan direction along an X axis as compared to a so-called standard resolution in a media advance direction along a Y axis. In one exemplary form the X axis dot-per-inch (dpi) resolution between columns is twice the dpi resolution of the Y axis resolution between rows.
In a preferred form a swath width defined by a nozzle array on a print cartridge enables an entire full height of a sequence of digital characters to be printed in a single pass of the print cartridge over a row of hybrid cells. For higher throughput, some embodiments employ bidirectional printing, while other embodiments provide lengthened nozzle arrays in order to print multiple rows of characters in a single pass of printhead(s) across the media. By providing each row of hybrid cells with a spaced apart resolution matching the nozzle pitch of the nozzle array, each row of the printable portion of the hybrid cell can be available for receiving marking dots during a single pass of the print cartridge.
If desirable a customized font may include a family of differently sized hybrid cells in order to provide prominence to certain items include in a printout. Also in some printing systems incorporating the customized fonts of the present invention, multiple printheads in one or more print cartridges can be respectively supplied with different color inks in order to distinguish between certain items in a printout. In other embodiments featuring more prominent displays of certain items, double and/or triple sequences of parallel lines can be used to form certain digitized characters of the font.
A fast print mode allows a minimal amount of ink to be deposited on relatively few pixels in each hybrid cell without unduly detracting from the legibility of the printed characters. In one aspect of the invention, such a print mode prevents marking drops from being deposited on adjacent pixels in a given row. Thus a solid appearing line or a partial area fill will have marking drops only on alternate pixels in a given row. However by changing the timing patterns on adjacent rows it is possible to achieve high legibility for diagonal and curved shapes without having to increase the firing frequency of the nozzles or other marking elements. The resulting digitized characters can therefore be constructed with various combinations of straight, slanted and curved lines without using an excessive amount of ink. In a preferred embodiment each individual line forming various upper and lower case alphanumeric characters is defined by a single sequence of marking dots.
The preferred external dimensions for a hybrid cell are defined to provide a shortened width dimension measured along the X axis. Thus the cell width is a fractional portion of the cell height measured along the Y axis. In one currently preferred embodiment the cell width is one-half of the cell height. Thus in an exemplary printing system using a print cartridge having 12 nozzles with a 96 dpi nozzle pitch which prints on a 96xc3x97192 pixel grid (i.e., 96 dpi in the Y axis direction and 192 dpi in the X axis direction), the height dimension of the hybrid cell would be 12 pixels high while the width dimension of the hybrid cell would also be 12 pixels wide.
Printable pixel areas are chosen to assure adequate spacing between characters on adjacent rows as well as adjacent columns. As a result a single print swath by one or more printheads across the receipt will create a single linear collection of characters, with all of the numeric monetary numerals and symbols precisely positioned both vertically and horizontally for easy visual perusal of the individual prices as well as the computed totals.
Where it is deemed necessary and desirable, differently sized cells can be incorporated into the same font in order to display some information more prominently than others. Also in order to provide such more prominent display, double and/or triple sequences of parallel lines can be used to form the various digitized characters of the font.
The invention therefore provides a high throughput printing system which may use low resolution printheads to create legible printouts of rasterized data using a hybrid font whyerein each digitized character can be formed by a minimal number of ink drops.